<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        div{
            background-color: darkcyan;
            width: 300px;
            height: 300px;
            /*border-left-width: 20px;*/
            /*border-left-color: blue;*/
            /*border-left-style: dashed;*/

            /*border-top: 20px red solid;*/

            /*border-bottom: 20px #8bc34a dotted;*/

            /*border-right: yellow 20px double;*/

            border: 20px #234567 solid;
        }
    </style>
</head>
<body>

<div>边框</div>

</body>
</html>